1. Field of the Invention
The present invention relates to an expandable network system and a redundant method for the same, in particular, the network system is formed with one or more sub-networks, and each sub-network has a plurality of network nodes. The system accomplishes fast redundancy by defining the role of each port, and re-defining the roles as the network system changes.
2. Description of Related Art
With growing of widespread applications of networks, the network safety and reliability is continually becomes more and more important, this is particularly so with ring-type networks for special applications. To avoid any interruption resulting from any unexpected event to the network, or to any connection failure of network device's damage, the conventional technology provides some schemes for redundancies.
In practice, at least one network switch is disposed on each node in a local area network for some applications or some other networks for industrial automatic systems. The relevant network devices in the network may be accessed via the network switch. Those network devices can be the networking devices, such as an industrial controller for an industrial automatic system, a conventional computer and a server. In which, an operator may perform a remote control or maintenance through the industrial controller.
Topological types for a variety of network architectures include linear-type, ring-type, bus-type, star-type, mesh-type, and tree-type. The ring-type network is configured to link the nodes in the network in series, and the first node is closed to the last one. Each node in the ring-type network may be communicated with any other node in the network through a ring-type transmission route. However, the transmitted data may be looped in the ring-type network circularly. New arrived data may not be delivered if old data is looped in the ring and occupying the bandwidth. The circular looping data may paralyze the network since it generates broadcast storm. One of the solutions to the program is to set a blocked port on a node in the ring-type network. This blocked port disallows the data to pass, and the mentioned looping data may not be endless.
Further, due to the inherent property of the ring-type network, it may be damaged as one of the nodes in the ring fails. The other nodes are also affected, and even meeting an overall failure. Therefore, it is very important to ensure the connectivity of the network. The conventional redundant scheme for the ring-type network is such as a Rapid Spanning Tree Protocol (RSTP) algorithm, which is used for stabilizing the data routing. According to the RSTP algorithm, when the blocked port is aware of any node or route damages, the predefined blocked port is transformed into a forward port, which allows the data to pass. The RSTP algorithm makes the whole system stay without obstruction. As long as the failed node or route recovers, the system can be restored to the initial state.
Regarding a redundant technology to a ring-type network with multiple rings, a conventional scheme provides a redundant scheme for the ring-type network shown in FIG. 1.
A plurality of network nodes 101, 102, 103, 104, 105, 106 shown in the drawing are separated to form two ring-type networks 11, 12. The two ring-type networks 11, 12 are interconnected over two connections 13, 14. The connection 13 is served by a network node 101 and the other network node 104. The connection 14 is made by interconnecting a network node 103 and a network node 106. In a normal operation, a major connection 13, for example, is regarded as the major route for delivering packets. If any connection meets abnormal situation, such as being broken, failure of node, a redundant connection 14, for example, will be immediately activated. The port states of nodes on each connection may also be changed in order to prevent any interruption of communication between the two ring-type networks 11, 12.
Since it needs time to repair the damaged route or restore the initial state in the above-mentioned technology, the conventional RSTP algorithm for switching the port state may not be quick enough. Therefore, the lost packets during the time to switch the port state may be many and conduct whole system's failure.